This invention relates to a video display apparatus in which a large number of luminous elements of the number equal to that of picture elements are arrayed in a plane for displaying a television image, a picture or letters are lighted in accordance with digitalized level adjusted light data, that is brightness data.
In such apparatus, the level of a light or image signal supplied to each display element is adjusted in many steps for example 64, and the interval of the light signal supplied to the luminous element is varied in accordance with the adjusted level, thus controlling the light quantity emitted by the luminous element.
A large scale image display apparatus installed on the outdoor, for example, a baseball ground, comprises several tens of thousands or more luminous elements. However, it is difficult to manufacture such large numbers of luminous elements to have the same luminescent characteristic when they are energized by the same operating power, so that it has been the conventional practice to individually measure the luminescent characteristic of respective elements and to provide individual light quantity adjusting circuits for respective luminous elements. Due to an extremely large number of the luminous elements used, measurements of their characteristics and adjustments of the light quantity adjusting circuits are not only troublesome but also expensive, which in turn increases the cost and size of the image display apparatus.